The present invention relates generally to bipolar devices, and more particularly, to a single event upset hardening technique for bipolar devices.
Satellites and other spacecraft are in widespread use for various purposes including scientific research and communications. These scientific and communications missions, however, cannot be accurately fulfilled without maintaining electronic data integrity. In many applications, the satellite relies upon electronic data to perform attitude and position corrections, diagnostic status checks, communication calculations and other functions. Without accurate electronic data, proper satellite function is hindered and at times adversely effected.
Integrated circuits (IC""s) used in computers and other electronic systems aboard space vehicles are susceptible to a phenomenon known as Single Event Upset, or SEU. Single Event Upset occurs when energetic particles, such as cosmic radiation, pass through an integrated circuit depositing stray charges in the device, causing one of its registers to be disrupted. This disruption may result in one or more data errors.
Several fault protection techniques, such as redundancy and error detection and correction, can be utilized to reduce the number of SEU""s that occur in the integrated circuits used aboard space vehicles. One technique is to increase the size of the registers, as a larger register requires a greater amount of stray charge for an SEU to occur. However, the resistance to Single Event Upset only increases linearly with area. Therefore, a rather large tenfold increase in the area of a register only improves the resistance to upset by ten times. This is in direct contrast to the current trend in technology, which is constantly reducing size and voltage required for electronic devices.
The disadvantages associated with these conventional single event upset fault protection techniques, such as limited use and/or cost penalties, have made it apparent that a new technique for hardening bipolar devices against single event upset faults is needed. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable single event upset hardening technique for bipolar devices. Another object of the invention is to reduce the charge collected in a bipolar device caused by energetic particles.
In one embodiment of the invention, a bipolar device hardened against single event upset includes a voltage source, a substrate, and a surface contact. The substrate includes a first collector region, a first base region and a first emitter region. The first collector region has a first collector voltage and a first voltage threshold. The first voltage threshold is the voltage at which a bipolar device connected to the first collector or first emitter becomes upset. When the first collector voltage drops below the first voltage threshold, the attached bipolar device becomes upset. The first base region is adjacent to the first collector region and the first emitter region is adjacent to the first base region. The surface contact is disposed on the substrate and is coupled to a voltage bias generated by the voltage source. The voltage bias is greater then the first voltage threshold so that the first collector voltage is prevented from dropping below the first voltage threshold due to energetic particle induced charge.
The present invention thus achieves an improved single event upset hardening technique for bipolar devices. The present invention is advantageous in that a single contact may be used to harden several bipolar devices.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.